At present most of the locks available on the market are mechanical in nature and are susceptible to picking by criminals. One great disadvantage of the mechanical locks has been noninterchangeability of the code in the field.
Recently some electronic locks have appeared in the market which use solenoids or electrical motors to activate the bolt mechanism. Such systems usually have the disadvantage, however, of unreliable mechanical operation of the locks, thereby preventing their wide usage. These systems also have direct solenoid or motor operated bolts, so that they require relatively large power. This disadvantage has prohibited locks incorporating them from being designed as self contained battery operated units. The present invention is directed to the problem of an electronic lock which overcomes the electromechanical interface problems between the electronics and the mechanical elements of the lock.
Briefly stated, in accordance with its invention, the above object is attained by providing an electronic locking system including means for sensing a key code, by means of optoelectronic, magnetic or other electrical means. The key code as sensed is compared to an internally stored code in the lock system. Depending upon the results of comparison and control commands on the key, the bolt mechanism of the lock may be activated and/or the internally stored code in the lock system may be changed to a new code.
In the locking system of the invention an electromechanical interface is provided between the bolt of the lock and the electrical portion of the lock system, thereby permitting very reliable operation of the lock. The locking system may be operated with battery power, since the battery is required only to activate the clutch and not to activate the bolt mechanism. The locking systems thereby does not rapidly drain the energy source, and may be operated over very long periods of time without replacement or recharging of the batteries. As a consequence, the lock system of the invention may be self contained and battery operated.
In a further feature of the invention, the lock key is operated only upon removal of the key from the lock. This arrangement eliminates the problems that occur when the operator forgets to remove the key from the lock. A key is thereby not available for use by unauthorized personnel.
In a still further feature of the invention, the locking system provides for multi-access level, such as master keys, floor keys, guest keys, and backup keys, and this feature may be effected in an inexpensive manner by employing a special control code of the keys directed to special portions of the memory of the locking system.
In a still further feature of the invention, the locking system incorporates a timer which switches power to power consuming circuits of a lock only during active operation of the lock. This feature, in addition to the above discussed clutch bolt mechanism, reduces the power consumption of the lock and thereby also facilitates operation of the lock by batteries.
In still further features of the invention, the lock system of the invention may be easily interfaced with an electronic alarm or security system and the code of the lock may be changed by special keys which do not permit access by way of the lock. The locking system of the invention is also adaptable for use with a key code to permit only a single entry by way of the lock, i.e. the code may be self-cancelling. The lock system of the invention may also be readily arranged under the control of a manual switch, to restrict lock operation to a selected number of access levels.